Western Bluebird

Sialia mexicana

In partly open terrain of the west, from valley farms and orchards to clearings in mountain pine forest, this bluebird is often common. In summer it is often seen perching alone on fence wires by open meadows, fluttering down to pluck insects from the grass. In winter, small flocks of Western Bluebirds are often heard flying overhead or seen feeding on berries in trees. Sometimes, as when juniper woods have heavy berry crops, the bluebirds may gather by the hundreds.

Conservation status

In recent decades, numbers have declined over much of range. Provision of birdhouses probably has not kept pace with loss of natural nest sites.

In partly open terrain of the west, from valley farms and orchards to clearings in mountain pine forest, this bluebird is often common. In summer it is often seen perching alone on fence wires by open meadows, fluttering down to pluck insects from the grass. In winter, small flocks of Western Bluebirds are often heard flying overhead or seen feeding on berries in trees. Sometimes, as when juniper woods have heavy berry crops, the bluebirds may gather by the hundreds.

Photo Gallery

Feeding Behavior

Often forages by perching fairly low and flying down to ground to capture insects, sometimes hovering briefly before pouncing. May catch insects in mid-air, or may seek them among foliage. Perches or flutters among branches to take berries.

Eggs

4-6, sometimes 3-8. Pale blue, unmarked; occasionally white. Incubation is by female, incubation period not well known. Young: Both parents bring food to nestlings. Age of young at first flight is not well known, probably between 2 and 3 weeks. Probably 2 broods per year.

Young

Both parents bring food to nestlings. Age of young at first flight is not well known, probably between 2 and 3 weeks. Probably 2 broods per year.

Diet

Mostly insects and berries. Insects make up majority of diet, especially in summer; feeds heavily on grasshoppers, caterpillars, beetles, ants, also many other insects. Berries and small fruits are important in diet especially in winter; among those eaten are fruits of mistletoe, juniper, and elderberry.

Nesting

Male typically arrives on breeding grounds before female, and defends nesting territory by singing. In courtship, male may flutter in front of female with wings and tail partly spread, while singing. Male may also feed female. Nest site is in cavity, such as natural hollow in oak or pine, old woodpecker hole, birdhouse, sometimes hole in building. Usually nests fairly low, rarely up to 50' above the ground. Nest in cavity is probably built mostly by female, but male may take part. Nest is a rather loose cup of twigs and weeds, lined with finer grass.

How climate change could affect this bird's range

In the broadest and most detailed study of its kind, Audubon scientists have used hundreds of thousands of citizen-science observations and sophisticated climate models to predict how birds in the U.S. and Canada will react to climate change.

Western Bluebird

Each map is a visual guide to where a particular bird species may find the climate conditions it needs to survive in the future. We call this the bird’s “climatic range.”

The colors indicate the season in which the bird may find suitable conditions— blue for winter, yellow for summer (breeding), and green for where they overlap (indicating their presence year-round).

The darker the shaded area, the more likely it is the bird species will find suitable climate conditions to survive there.

The outline of the approximate current range for each season remains fixed in each frame, allowing you to compare how the range will expand, contract, or shift in the future.

The first frame of the animation shows where the bird can find a suitable climate today (based on data from 2000). The next three frames predict where this bird’s suitable climate may shift in the future—one frame each for 2020, 2050, and 2080.

You can play or pause the animation with the orange button in the lower left, or select an individual frame to study by clicking on its year.

The darker the color, the more favorable the climate conditions are for survival. The outlined areas represent approximate current range for each season. More on reading these maps.